See also my answer to a related question. You have time to plant and harvest spinach, kale, lettuce, and if you're willing to provide a little frost protection you can probably get broccoli and early cabbage, among others.
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bstpierreSep 23 '11 at 3:09

3 Answers
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Here in North Texas we get frosts in winter but most people would not call it a cool climate - we had highs over 100F for most of 3 months this summer (yes August was the hottest average month for any US State ever recorded).

What you are thinking of as "cool" is probably what I usually describe as "temperate" - typically 40-60 degrees north - places like Washington State, Maine, the UK, France, etc. They get frosts but don't get hot. However "cool" is definitely a relative term: in Costa Rica we'd use the term for areas at altitude which are cooler than the Central Valley.

So it depends on your reference point, but yes I'd expect a cool climate plant to have a good frost tolerance - but if you were buying a plant labeled as "cool climate" in Hong Kong, or Central America (say), then it probably wouldn't...

I see you're in Newfoundland/Labrador: So I'd definitely call that a cool climate. I would expect your vegetable growing season is from spring through to autumn. Similar to what we'd get in the UK, although if your last frosts are in January you may be able to plant stuff earlier (eg. February).

Cool climate plants are plants that grow best during the cool, damp time of year starting near the last frost in spring, and sometimes in the wet period of fall. The plants that grow best during this time are naturally tolerant to some frost. Read the seed packet instructions for the information needed to properly grow these plants.

Cool season plants thrive in cool temperatures (40°F to 70°F daytime temperatures) and are somewhat tolerant of light frosts...

Warm season plants thrive in warm temperatures (65°F to 90°F daytime temperatures) and are intolerant of cool temperatures...

Some vegetables can take Wintertime, cold (freezing) weather much better than others, in fact some only reach their full potential (flavour) if they go through a few "light" freezes or a complete Winter (can be over Wintered in the ground) eg

The use of "cool climate" in the question and "winwaed" opening comment, "How long is a piece of string?" :-) had me wondering if there was a definitive definition of "cool climate" used in horticultural...

I couldn't find one online (that's not to say there isn't one).

I asked some "experts" on twitter, no one could point me to a definitive definition.

I'm currently left thinking "cool climate" isn't a good term to be used in horticulture, it's too open ended...

Below are a few responses I got on twitter when I asked, "Help, looking for a definitive definition of "cool climate" used in horticultural..."

Well that is pretty subjective (used a lot in the US, where there is such a huge difference across the country).

"Cool Temperate" is the ecological term for the vegetation zone that most of the UK lies in. It is the area of deciduous forest that runs across Europe. To the south is the "Warm Temperate" or Mediterranean zone, and to the north is the "Boreal" or coniferous forest zone. /via Cool Temperate

"Cool season" crops that do best with daytime highs, max out around 60-70°F, with nighttime lows in the 40s-50s°F and can tolerate light frost. /courtesy of University of Illinois Extension Horticultural Educator, Jennifer Schultz Nelson, Ph.D.

While there's no "definitive" standard, our rough definition ranges from just above the frost threshold up to the mid-70s°F /via Missouri Botanical Garden